Vajrasattva: Guiding Instructions on the One Hundred Syllable Mantra of Dro Kālacakra by Jetsun Tāranātha and Bamda Gelek Gyamtso. Translated and edited by Adele Tomlin (Dakini Publications, 2020). Available for free download here.
Meaning of the Vajra Heruka Hundred Syllable Mantra according to Bamda Gelek Gyatso